Regulation of the interaction between carboxymethyl starch and whey protein isolate by tannin: Effects on their colonic targeting and stimulation of satiety hormone secretion.

Starch-protein interactions are widely used to regulate the digestibility of starch and protein in the upper gastrointestinal tract. This study prepared carboxymethyl starch (CMS)-whey protein isolate (WPI) crosslinked complexes (CMS-WPI/TA) by regulating the interaction in the CMS-WPI system by tannin (TA), and explored the effects of the complexes on the secretion of satiety hormones. The results showed that after the addition of TA, the interaction in CMS-WPI system shifted from electrostatic interactions to hydrogen bonding and van der Waals interactions, forming more compact, uniform, and ordered TA-crosslinked complexes. In vitro simulated digestion results indicated that the digestion rates of CMS and WPI in CMS-WPI/TA2 in the upper gastrointestinal tract were reduced to 5.77 % and 26.33 %, respectively, thus permitting most of the CMS and WPI to reach the colon and be degraded by the gut microbiota into short-chain fatty acids, peptides, and amino acids. These metabolic products can stimulate the sustained secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) by L cells, with their secretion increased by 101.02 % and 106.30 % compared to the blank group, respectively. The TA-crosslinked complexes also increased the abundance of SCFA-producing bacteria such as Dialister and Blautia, and reduced the abundance of harmful gut microbiota such as Collinsella. The results of this study provide new insights into regulating starch-protein interactions to improve their resistance to digestion and contribute to the development of functional foods that are beneficial to the human gut microbiota and enhance satiety.